Final answer:
Lioresal (Baclofen) is the most beneficial oral agent for the treatment of limb spasticity related to multiple sclerosis.
Step-by-step explanation:
The question asks which oral agent would be most beneficial in the treatment of limb spasticity related to multiple sclerosis. Among the options given, C. Lioresal (also known as Baclofen) is the correct answer. Lioresal is a muscle relaxant and antispastic agent that is commonly used to reduce and relieve the frequency and severity of muscle spasms that can occur as a result of multiple sclerosis. Baclofen is a muscle relaxant that is commonly used to manage spasticity associated with conditions like multiple sclerosis. It acts on the central nervous system to reduce muscle spasms and tightness. Options A, B, D, and E are not typically used as first-line agents for spasticity related to multiple sclerosis. Clonazepam and phenytoin are more commonly associated with seizure disorders, phenobarbital is a barbiturate with sedative properties, and cyproheptadine is an antihistamine with mild antiserotonergic effects, and they are not typically used as primary treatments for spasticity.